Human beings have had a long battle against cancer. Because the disease is so widespread, manifests itself in so many different ways and is so relentless, the potential market for effective cancer therapies is enormous. It is estimated that 10 million people in the U.S. either have or have had cancer. The National Cancer Institute (NCI) projects that in 1995, some 1.2 million new cases of cancer will be diagnosed in the United States, and that 538,000 people will die of the disease.
Cancer is currently treated, with a low degree of success, with combinations of surgery, chemotherapy and radiation. The reason of the low degrees of success in cancer chemotherapy is as the following: current chemotherapeutic approaches target rapidly dividing tumor cells. This approach is ineffective when the cancer is dormant or growing slowly. Such treatments also affect other, non-cancerous cells that divide rapidly, causing harmful side effects.
Only in the last several years has a new approach emerged in the battle against cancer. This approach is based on the newly discovered biological phenomenon called “Apoptosis”. Apoptosis is also called “programmed cell death” or “cell suicide”. (Krammer, et al., “Apoptosis in the APO-1 System”, Apoptosis: The molecular Basis of Cell Death, pp. 87-99 Cold Spring Harbor Laboratory Press, 1991). In contrast to the cell death caused by cell injury, apoptosis is an active process of gene-directed, cellular self-destruction and that it serves a biologically meaningful function. (Kerr, J. F. R and J. Searle J. Pathol. 107:41, 1971).
One of the examples of the biologically meaningful functions of apoptosis is the morphogenesis of embryo. (Michaelson, J. Biol. Rev. 62:115, 1987). Just like the sculpturing of a sculpture, which needs the addition as well as removal of clay, the organ formation (Morphogenesis) of an embryo relies on cell growth (addition of clay) as well as cell death (removal of clay). As a matter of fact, apoptosis plays a key role in the human body from the early stages of embryonic development through to the inevitable decline associated with old age. (Wyllie, A. H. Int. Rev. Cytol. 68:251, 1980). The normal function of the immune, gastrointestinal and hematopoietic system relies on the normal function of apoptosis. When the normal function of apoptosis goes awry, the cause or the result can be one of a number of diseases, including: cancer, viral infections, auto-immune disease/allergies, neuro-degeneration or cardiovascular diseases.
Because of the versatility of apoptosis involved in human diseases, apoptosis is becoming a prominent buzzword in the pharmaceutical research field. Huge amounts of time and money are being spent in an attempt to understand how it works, how it can be encouraged or inhibited and what this means for practical medicine. A handful of companies have been formed with the prime direction of turning work in this nascent field into marketable pharmaceutical products. The emergence of a core of innovative young companies combined with the tentative steps being taken by established industrial players are certain to make apoptosis research one of the fastest-growing and most promising areas of medical study of the 1990's.
The idea that cancer may be caused by insufficient apoptosis merged only recently (Cope, F. O. and Wille, J. J., “Apoptosis”: The Molecular Basis of Cell Death, Cold Spring Harbor Laboratory Press, p. 61, 1991). This idea however, opens a door for a new concept in cancer therapy—cancer cells may be killed by encouraging apoptosis. Apoptosis modulation, based on the processes present in normal development, is a potential mechanism for controlling the growth of tumor cells. Restoring apoptosis in tumor cells is an attractive approach because, at least in theory, it would teach the cells to commit suicide.
Nevertheless, since the objective of cancer treatment is to kill cancer cells without killing the host, although apoptosis may open a new door for cancer therapy by inducing apoptosis in tumor cells, the success of this treatment is still dependent on the availability of drugs that can selectively induce apoptosis in tumor cells without affecting normal cells. In this patent application, we describe the methods for the isolation of proteins that specifically induce apoptosis in cancer cells without effect in normal cells. These proteins may present a new class of anticancer drugs that induce apoptosis in cancer cells, which may offer a breakthrough in cancer therapy.